Use external/safe-iop to check for overflows on arithmetic
operations.
Also remove an unnecessary copy of Vector/SharedBuffer from
codeflinger and use the copy from libutils instead.
Note that some of the unit tests are somewhat useless due to
test-runner limitations : gtest's ability to filter on abort message
doesn't work when combined with messages formatted by android's logging
system.
bug: 22953624
(cherry picked from commit c609c31fb5)
Change-Id: I673b7ab142bed4fcba9159a00a65cf6bca6b1f6c
b638126ed3